Merge tag 'lkdtm-next' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux into char-misc-testing

Kees writes:

New tests for prior memory protections (EXEC_RODATA), new tests for upcoming
kernel self-protections (USERCOPY_HEAP_SIZE_TO, USERCOPY_HEAP_SIZE_FROM,
USERCOPY_HEAP_FLAG_TO, USERCOPY_HEAP_FLAG_FROM, USERCOPY_STACK_FRAME_TO,
USERCOPY_STACK_FRAME_FROM, USERCOPY_STACK_BEYOND), and updated tests
(ATOMIC_UNDERFLOW, ATOMIC_OVERFLOW).

MAINTAINERS

@@ -6954,7 +6954,7 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching.git
 LINUX KERNEL DUMP TEST MODULE (LKDTM)
 M:	Kees Cook <keescook@chromium.org>
 S:	Maintained
-F:	drivers/misc/lkdtm.c
+F:	drivers/misc/lkdtm*
 
 LLC (802.2)
 M:	Arnaldo Carvalho de Melo <acme@ghostprotocols.net>

drivers/misc/Makefile

@@ -57,3 +57,13 @@ obj-$(CONFIG_ECHO)		+= echo/
 obj-$(CONFIG_VEXPRESS_SYSCFG)	+= vexpress-syscfg.o
 obj-$(CONFIG_CXL_BASE)		+= cxl/
 obj-$(CONFIG_PANEL)             += panel.o
+
+lkdtm-$(CONFIG_LKDTM)		+= lkdtm_core.o
+lkdtm-$(CONFIG_LKDTM)		+= lkdtm_rodata_objcopy.o
+
+OBJCOPYFLAGS :=
+OBJCOPYFLAGS_lkdtm_rodata_objcopy.o := \
+			--set-section-flags .text=alloc,readonly \
+			--rename-section .text=.rodata
+$(obj)/lkdtm_rodata_objcopy.o: $(obj)/lkdtm_rodata.o
+	$(call if_changed,objcopy)

drivers/misc/lkdtm.h

@@ -0,0 +1,6 @@
+#ifndef __LKDTM_H
+#define __LKDTM_H
+
+void lkdtm_rodata_do_nothing(void);
+
+#endif

drivers/misc/lkdtm.c → drivers/misc/lkdtm_core.c

@@ -1,5 +1,9 @@
 /*
- * Kprobe module for testing crash dumps
+ * Linux Kernel Dump Test Module for testing kernel crashes conditions:
+ * induces system failures at predefined crashpoints and under predefined
+ * operational conditions in order to evaluate the reliability of kernel
+ * sanity checking and crash dumps obtained using different dumping
+ * solutions.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -19,10 +23,6 @@
  *
  * Author: Ankita Garg <ankita@in.ibm.com>
  *
- * This module induces system failures at predefined crashpoints to
- * evaluate the reliability of crash dumps obtained using different dumping
- * solutions.
- *
  * It is adapted from the Linux Kernel Dump Test Tool by
  * Fernando Luis Vazquez Cao <http://lkdtt.sourceforge.net>
  *
@@ -30,7 +30,7 @@
  *
  * See Documentation/fault-injection/provoke-crashes.txt for instructions
  */
-#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#define pr_fmt(fmt) "lkdtm: " fmt
 
 #include <linux/kernel.h>
 #include <linux/fs.h>
@@ -52,6 +52,8 @@
 #include <linux/ide.h>
 #endif
 
+#include "lkdtm.h"
+
 /*
  * Make sure our attempts to over run the kernel stack doesn't trigger
  * a compiler warning when CONFIG_FRAME_WARN is set. Then make sure we
@@ -103,12 +105,21 @@ enum ctype {
 	CT_EXEC_STACK,
 	CT_EXEC_KMALLOC,
 	CT_EXEC_VMALLOC,
+	CT_EXEC_RODATA,
 	CT_EXEC_USERSPACE,
 	CT_ACCESS_USERSPACE,
 	CT_WRITE_RO,
 	CT_WRITE_RO_AFTER_INIT,
 	CT_WRITE_KERN,
-	CT_WRAP_ATOMIC
+	CT_ATOMIC_UNDERFLOW,
+	CT_ATOMIC_OVERFLOW,
+	CT_USERCOPY_HEAP_SIZE_TO,
+	CT_USERCOPY_HEAP_SIZE_FROM,
+	CT_USERCOPY_HEAP_FLAG_TO,
+	CT_USERCOPY_HEAP_FLAG_FROM,
+	CT_USERCOPY_STACK_FRAME_TO,
+	CT_USERCOPY_STACK_FRAME_FROM,
+	CT_USERCOPY_STACK_BEYOND,
 };
 
 static char* cp_name[] = {
@@ -145,12 +156,21 @@ static char* cp_type[] = {
 	"EXEC_STACK",
 	"EXEC_KMALLOC",
 	"EXEC_VMALLOC",
+	"EXEC_RODATA",
 	"EXEC_USERSPACE",
 	"ACCESS_USERSPACE",
 	"WRITE_RO",
 	"WRITE_RO_AFTER_INIT",
 	"WRITE_KERN",
-	"WRAP_ATOMIC"
+	"ATOMIC_UNDERFLOW",
+	"ATOMIC_OVERFLOW",
+	"USERCOPY_HEAP_SIZE_TO",
+	"USERCOPY_HEAP_SIZE_FROM",
+	"USERCOPY_HEAP_FLAG_TO",
+	"USERCOPY_HEAP_FLAG_FROM",
+	"USERCOPY_STACK_FRAME_TO",
+	"USERCOPY_STACK_FRAME_FROM",
+	"USERCOPY_STACK_BEYOND",
 };
 
 static struct jprobe lkdtm;
@@ -162,6 +182,8 @@ static char* cpoint_name;
 static char* cpoint_type;
 static int cpoint_count = DEFAULT_COUNT;
 static int recur_count = REC_NUM_DEFAULT;
+static int alloc_size = 1024;
+static size_t cache_size;
 
 static enum cname cpoint = CN_INVALID;
 static enum ctype cptype = CT_NONE;
@@ -170,7 +192,9 @@ static DEFINE_SPINLOCK(count_lock);
 static DEFINE_SPINLOCK(lock_me_up);
 
 static u8 data_area[EXEC_SIZE];
+static struct kmem_cache *bad_cache;
 
+static const unsigned char test_text[] = "This is a test.\n";
 static const unsigned long rodata = 0xAA55AA55;
 static unsigned long ro_after_init __ro_after_init = 0x55AA5500;
 
@@ -184,6 +208,9 @@ MODULE_PARM_DESC(cpoint_type, " Crash Point Type, action to be taken on "\
 module_param(cpoint_count, int, 0644);
 MODULE_PARM_DESC(cpoint_count, " Crash Point Count, number of times the "\
 				"crash point is to be hit to trigger action");
+module_param(alloc_size, int, 0644);
+MODULE_PARM_DESC(alloc_size, " Size of allocation for user copy tests "\
+			     "(from 1 to PAGE_SIZE)");
 
 static unsigned int jp_do_irq(unsigned int irq)
 {
@@ -346,15 +373,18 @@ static noinline void corrupt_stack(void)
 	memset((void *)data, 0, 64);
 }
 
-static void noinline execute_location(void *dst)
+static noinline void execute_location(void *dst, bool write)
 {
 	void (*func)(void) = dst;
 
 	pr_info("attempting ok execution at %p\n", do_nothing);
 	do_nothing();
 
-	memcpy(dst, do_nothing, EXEC_SIZE);
-	flush_icache_range((unsigned long)dst, (unsigned long)dst + EXEC_SIZE);
+	if (write) {
+		memcpy(dst, do_nothing, EXEC_SIZE);
+		flush_icache_range((unsigned long)dst,
+				   (unsigned long)dst + EXEC_SIZE);
+	}
 	pr_info("attempting bad execution at %p\n", func);
 	func();
 }
@@ -374,6 +404,228 @@ static void execute_user_location(void *dst)
 	func();
 }
 
+/*
+ * Instead of adding -Wno-return-local-addr, just pass the stack address
+ * through a function to obfuscate it from the compiler.
+ */
+static noinline unsigned char *trick_compiler(unsigned char *stack)
+{
+	return stack + 0;
+}
+
+static noinline unsigned char *do_usercopy_stack_callee(int value)
+{
+	unsigned char buf[32];
+	int i;
+
+	/* Exercise stack to avoid everything living in registers. */
+	for (i = 0; i < sizeof(buf); i++) {
+		buf[i] = value & 0xff;
+	}
+
+	return trick_compiler(buf);
+}
+
+static noinline void do_usercopy_stack(bool to_user, bool bad_frame)
+{
+	unsigned long user_addr;
+	unsigned char good_stack[32];
+	unsigned char *bad_stack;
+	int i;
+
+	/* Exercise stack to avoid everything living in registers. */
+	for (i = 0; i < sizeof(good_stack); i++)
+		good_stack[i] = test_text[i % sizeof(test_text)];
+
+	/* This is a pointer to outside our current stack frame. */
+	if (bad_frame) {
+		bad_stack = do_usercopy_stack_callee(alloc_size);
+	} else {
+		/* Put start address just inside stack. */
+		bad_stack = task_stack_page(current) + THREAD_SIZE;
+		bad_stack -= sizeof(unsigned long);
+	}
+
+	user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
+			    PROT_READ | PROT_WRITE | PROT_EXEC,
+			    MAP_ANONYMOUS | MAP_PRIVATE, 0);
+	if (user_addr >= TASK_SIZE) {
+		pr_warn("Failed to allocate user memory\n");
+		return;
+	}
+
+	if (to_user) {
+		pr_info("attempting good copy_to_user of local stack\n");
+		if (copy_to_user((void __user *)user_addr, good_stack,
+				 sizeof(good_stack))) {
+			pr_warn("copy_to_user failed unexpectedly?!\n");
+			goto free_user;
+		}
+
+		pr_info("attempting bad copy_to_user of distant stack\n");
+		if (copy_to_user((void __user *)user_addr, bad_stack,
+				 sizeof(good_stack))) {
+			pr_warn("copy_to_user failed, but lacked Oops\n");
+			goto free_user;
+		}
+	} else {
+		/*
+		 * There isn't a safe way to not be protected by usercopy
+		 * if we're going to write to another thread's stack.
+		 */
+		if (!bad_frame)
+			goto free_user;
+
+		pr_info("attempting good copy_from_user of local stack\n");
+		if (copy_from_user(good_stack, (void __user *)user_addr,
+				   sizeof(good_stack))) {
+			pr_warn("copy_from_user failed unexpectedly?!\n");
+			goto free_user;
+		}
+
+		pr_info("attempting bad copy_from_user of distant stack\n");
+		if (copy_from_user(bad_stack, (void __user *)user_addr,
+				   sizeof(good_stack))) {
+			pr_warn("copy_from_user failed, but lacked Oops\n");
+			goto free_user;
+		}
+	}
+
+free_user:
+	vm_munmap(user_addr, PAGE_SIZE);
+}
+
+static void do_usercopy_heap_size(bool to_user)
+{
+	unsigned long user_addr;
+	unsigned char *one, *two;
+	size_t size = clamp_t(int, alloc_size, 1, PAGE_SIZE);
+
+	one = kmalloc(size, GFP_KERNEL);
+	two = kmalloc(size, GFP_KERNEL);
+	if (!one || !two) {
+		pr_warn("Failed to allocate kernel memory\n");
+		goto free_kernel;
+	}
+
+	user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
+			    PROT_READ | PROT_WRITE | PROT_EXEC,
+			    MAP_ANONYMOUS | MAP_PRIVATE, 0);
+	if (user_addr >= TASK_SIZE) {
+		pr_warn("Failed to allocate user memory\n");
+		goto free_kernel;
+	}
+
+	memset(one, 'A', size);
+	memset(two, 'B', size);
+
+	if (to_user) {
+		pr_info("attempting good copy_to_user of correct size\n");
+		if (copy_to_user((void __user *)user_addr, one, size)) {
+			pr_warn("copy_to_user failed unexpectedly?!\n");
+			goto free_user;
+		}
+
+		pr_info("attempting bad copy_to_user of too large size\n");
+		if (copy_to_user((void __user *)user_addr, one, 2 * size)) {
+			pr_warn("copy_to_user failed, but lacked Oops\n");
+			goto free_user;
+		}
+	} else {
+		pr_info("attempting good copy_from_user of correct size\n");
+		if (copy_from_user(one, (void __user *)user_addr,
+				   size)) {
+			pr_warn("copy_from_user failed unexpectedly?!\n");
+			goto free_user;
+		}
+
+		pr_info("attempting bad copy_from_user of too large size\n");
+		if (copy_from_user(one, (void __user *)user_addr, 2 * size)) {
+			pr_warn("copy_from_user failed, but lacked Oops\n");
+			goto free_user;
+		}
+	}
+
+free_user:
+	vm_munmap(user_addr, PAGE_SIZE);
+free_kernel:
+	kfree(one);
+	kfree(two);
+}
+
+static void do_usercopy_heap_flag(bool to_user)
+{
+	unsigned long user_addr;
+	unsigned char *good_buf = NULL;
+	unsigned char *bad_buf = NULL;
+
+	/* Make sure cache was prepared. */
+	if (!bad_cache) {
+		pr_warn("Failed to allocate kernel cache\n");
+		return;
+	}
+
+	/*
+	 * Allocate one buffer from each cache (kmalloc will have the
+	 * SLAB_USERCOPY flag already, but "bad_cache" won't).
+	 */
+	good_buf = kmalloc(cache_size, GFP_KERNEL);
+	bad_buf = kmem_cache_alloc(bad_cache, GFP_KERNEL);
+	if (!good_buf || !bad_buf) {
+		pr_warn("Failed to allocate buffers from caches\n");
+		goto free_alloc;
+	}
+
+	/* Allocate user memory we'll poke at. */
+	user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
+			    PROT_READ | PROT_WRITE | PROT_EXEC,
+			    MAP_ANONYMOUS | MAP_PRIVATE, 0);
+	if (user_addr >= TASK_SIZE) {
+		pr_warn("Failed to allocate user memory\n");
+		goto free_alloc;
+	}
+
+	memset(good_buf, 'A', cache_size);
+	memset(bad_buf, 'B', cache_size);
+
+	if (to_user) {
+		pr_info("attempting good copy_to_user with SLAB_USERCOPY\n");
+		if (copy_to_user((void __user *)user_addr, good_buf,
+				 cache_size)) {
+			pr_warn("copy_to_user failed unexpectedly?!\n");
+			goto free_user;
+		}
+
+		pr_info("attempting bad copy_to_user w/o SLAB_USERCOPY\n");
+		if (copy_to_user((void __user *)user_addr, bad_buf,
+				 cache_size)) {
+			pr_warn("copy_to_user failed, but lacked Oops\n");
+			goto free_user;
+		}
+	} else {
+		pr_info("attempting good copy_from_user with SLAB_USERCOPY\n");
+		if (copy_from_user(good_buf, (void __user *)user_addr,
+				   cache_size)) {
+			pr_warn("copy_from_user failed unexpectedly?!\n");
+			goto free_user;
+		}
+
+		pr_info("attempting bad copy_from_user w/o SLAB_USERCOPY\n");
+		if (copy_from_user(bad_buf, (void __user *)user_addr,
+				   cache_size)) {
+			pr_warn("copy_from_user failed, but lacked Oops\n");
+			goto free_user;
+		}
+	}
+
+free_user:
+	vm_munmap(user_addr, PAGE_SIZE);
+free_alloc:
+	if (bad_buf)
+		kmem_cache_free(bad_cache, bad_buf);
+	kfree(good_buf);
+}
+
 static void lkdtm_do_action(enum ctype which)
 {
 	switch (which) {
@@ -551,25 +803,28 @@ static void lkdtm_do_action(enum ctype which)
 		schedule();
 		break;
 	case CT_EXEC_DATA:
-		execute_location(data_area);
+		execute_location(data_area, true);
 		break;
 	case CT_EXEC_STACK: {
 		u8 stack_area[EXEC_SIZE];
-		execute_location(stack_area);
+		execute_location(stack_area, true);
 		break;
 	}
 	case CT_EXEC_KMALLOC: {
 		u32 *kmalloc_area = kmalloc(EXEC_SIZE, GFP_KERNEL);
-		execute_location(kmalloc_area);
+		execute_location(kmalloc_area, true);
 		kfree(kmalloc_area);
 		break;
 	}
 	case CT_EXEC_VMALLOC: {
 		u32 *vmalloc_area = vmalloc(EXEC_SIZE);
-		execute_location(vmalloc_area);
+		execute_location(vmalloc_area, true);
 		vfree(vmalloc_area);
 		break;
 	}
+	case CT_EXEC_RODATA:
+		execute_location(lkdtm_rodata_do_nothing, false);
+		break;
 	case CT_EXEC_USERSPACE: {
 		unsigned long user_addr;
 
@@ -658,17 +913,50 @@ static void lkdtm_do_action(enum ctype which)
 		do_overwritten();
 		break;
 	}
-	case CT_WRAP_ATOMIC: {
+	case CT_ATOMIC_UNDERFLOW: {
 		atomic_t under = ATOMIC_INIT(INT_MIN);
-		atomic_t over = ATOMIC_INIT(INT_MAX);
 
-		pr_info("attempting atomic underflow\n");
+		pr_info("attempting good atomic increment\n");
+		atomic_inc(&under);
+		atomic_dec(&under);
+
+		pr_info("attempting bad atomic underflow\n");
 		atomic_dec(&under);
-		pr_info("attempting atomic overflow\n");
+		break;
+	}
+	case CT_ATOMIC_OVERFLOW: {
+		atomic_t over = ATOMIC_INIT(INT_MAX);
+
+		pr_info("attempting good atomic decrement\n");
+		atomic_dec(&over);
+		atomic_inc(&over);
+
+		pr_info("attempting bad atomic overflow\n");
 		atomic_inc(&over);
 
 		return;
 	}
+	case CT_USERCOPY_HEAP_SIZE_TO:
+		do_usercopy_heap_size(true);
+		break;
+	case CT_USERCOPY_HEAP_SIZE_FROM:
+		do_usercopy_heap_size(false);
+		break;
+	case CT_USERCOPY_HEAP_FLAG_TO:
+		do_usercopy_heap_flag(true);
+		break;
+	case CT_USERCOPY_HEAP_FLAG_FROM:
+		do_usercopy_heap_flag(false);
+		break;
+	case CT_USERCOPY_STACK_FRAME_TO:
+		do_usercopy_stack(true, true);
+		break;
+	case CT_USERCOPY_STACK_FRAME_FROM:
+		do_usercopy_stack(false, true);
+		break;
+	case CT_USERCOPY_STACK_BEYOND:
+		do_usercopy_stack(true, false);
+		break;
 	case CT_NONE:
 	default:
 		break;
@@ -961,6 +1249,11 @@ static int __init lkdtm_module_init(void)
 	/* Make sure we can write to __ro_after_init values during __init */
 	ro_after_init |= 0xAA;
 
+	/* Prepare cache that lacks SLAB_USERCOPY flag. */
+	cache_size = clamp_t(int, alloc_size, 1, PAGE_SIZE);
+	bad_cache = kmem_cache_create("lkdtm-no-usercopy", cache_size, 0,
+				      0, NULL);
+
 	/* Register debugfs interface */
 	lkdtm_debugfs_root = debugfs_create_dir("provoke-crash", NULL);
 	if (!lkdtm_debugfs_root) {
@@ -1012,6 +1305,8 @@ static void __exit lkdtm_module_exit(void)
 {
 	debugfs_remove_recursive(lkdtm_debugfs_root);
 
+	kmem_cache_destroy(bad_cache);
+
 	unregister_jprobe(&lkdtm);
 	pr_info("Crash point unregistered\n");
 }

drivers/misc/lkdtm_rodata.c

@@ -0,0 +1,10 @@
+/*
+ * This includes functions that are meant to live entirely in .rodata
+ * (via objcopy tricks), to validate the non-executability of .rodata.
+ */
+#include <linux/kernel.h>
+
+void lkdtm_rodata_do_nothing(void)
+{
+	/* Does nothing. We just want an architecture agnostic "return". */
+}